Your students will love this colorful demonstration which is always a teacher favorite at science conventions. A colorless solution is added to each of six seemingly empty beakers. A second colorless solution is then added and each of the six resulting solutions turns a different color of the rainbow. Add more of the first solution and the rainbow of colors disappears. Challenge your students to explain these amazing observations.

The secret is the small amount of indicator or mixture of indicators placed in each beaker before the demonstration. The first solution is hydrochloric acid which keeps the indicators colorless. The second solution is sodium hydroxide which raises the pH and activates the indicators causing a spectrum of color to appear. Enough materials are included to perform the demonstration seven times.